1. Field of the Invention
The present general inventive concept relates to an autostereoscopic display that is switchable between three dimensional (3D) and two dimensional (2D) modes of operation, and more particularly, to an improved 2D/3D switchable autostereoscopic display.
2. Description of the Related Art
In general, autostereoscopic displays are used in game machines, computer monitors, notebook displays, mobile phones, and other applications to produce stereoscopic images.
Autostereoscopic displays are typically mechanically switched between a two dimensional (2D) mode and a three dimensional (3D) mode to selectively provide a 2D image or a 3D image according to an image signal. Various types of switchable autostereoscopic displays have been developed.
For example, U.S. Pat. No. 5,500,765, entitled “convertible 2D/3D autostereoscopic display” and invented by Eichenlaub, discloses a conventional 2D/3D switchable autostereoscopic display using a lenticular parallax element, wherein switching from the 3D mode to the 2D mode is achieved by attaching a complementary lenticular sheet having a negative refractive power to the lenticular parallax element, which has a positive refractive power. The attached complementary lenticular sheet compensates optical power of the lenticular parallax element, such that a 2D image can be seen with full resolution on an image panel. To provide the 2D/3D switching, the conventional display has the screen sized complementary lenticular sheet mounted on hinges, which allows for the complementary lenticular sheet to be attached and detached by rotation. Accordingly, the conventional display is complex in structure and the complementary lenticular sheet, which is rotated on the hinges, requires a large amount of free space within and around the conventional display, thereby increasing an overall size of the conventional display.
U.S. Pat. No. 6,437,915, entitled “parallax barrier, display, passive polarization modulating optical element, and method of making such an element” and invented by Moseley et al., discloses another conventional 2D/3D switchable display based on a latent parallax barrier, which is activated by attaching a polarizer sheet on a display screen.
FIG. 1 is a perspective view of a conventional on-off switchable parallax barrier that uses a removable polarization sheet as disclosed in U.S. Pat. No. 6,437,915. Referring to FIG. 1, the conventional parallax barrier of the display includes a polarization modifying layer 10, and a polarizer in the form of a polarization sheet 11. The polarization modifying layer 10 includes aperture regions 12 in the form of parallel elongated slit regions arranged to rotate a linear polarization of incoming light 13 by 90 degrees. The aperture regions 12 are separated by barrier regions 14, which are arranged so as not to affect the polarization of the incoming light 13.
When the conventional parallax barrier is disposed in front of a liquid crystal display (LCD) of a thin film transistor (TFT) type, light output from the LCD is polarized in a direction indicated by arrow A.
The polarization sheet 11 has a polarization direction indicated by arrow B, which is perpendicular to a polarization direction A of incident light. However, the polarization direction B is parallel to the polarization direction of light passing through the aperture regions 12 such that the conventional parallax barrier operates in a barrier mode and incident light is transmitted through the aperture regions 12 while being substantially blocked or extinguished at parts of the conventional parallax barrier defined by the barrier regions 14. In order to operate the conventional parallax barrier in a non-barrier mode, the polarization sheet 11 is disabled, for instance, by being removed. In the non barrier-mode, the aperture regions 12 are substantially invisible because they are not analyzed by the polarization sheet 11.
FIGS. 2A through 2C illustrate conventional arrangements of a polarization sheet and the conventional parallax barrier.
Referring to FIG. 2A, a polarization sheet 21 is attached to a stereoscopic display 20 by double hinges 25. This allows the polarization sheet 21 to be rotated over a front of the display 20. In this case, a space for moving the polarization sheet 21 mounted on the hinges 25 becomes necessary, thereby leading to a bulky and complex structure.
Referring to FIG. 2B, a polarization sheet is formed on a transparent film 27 having a longitudinal region which is transparent and non-polarizing. The transparent film 27 is wound on rollers 29 that are disposed on either side of an LCD and a polarization modifying layer. The rollers 29 are driven for instance by an electric motor, so that a polarizing region of the polarization sheet or the transparent non-polarizing region of the film 27 may be disposed in front of the LCD.
When the transparent film 27 is wound on the rollers 29, the rollers 29 and the electric motor for driving the rollers 29 should be disposed on a body of the conventional display. Consequently, the conventional display is complex and is difficult to use.
FIG. 2C illustrates another arrangement to switch between the 3D and 2D modes of operation. Referring to FIG. 2C, a polarization sheet is installed in front of an LCD and a layer is disposed to be rotatable about an axis perpendicular to the polarization sheet.
The conventional display disclosed in U.S. Pat. No. 6,437,915 can switch between the 2D and 3D modes by rotating or rolling the polarization sheet 11. However, in this case, the overall size of the conventional display is significantly larger than a size of the display screen. Rotation of the polarization sheet 11 also requires a large space around the display screen and does not provide complete invisibility of the conventional parallax barrier structure.